ACI 318-19 Changes to the Concrete Design Standard-Strut-and-Tie Method

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Video Summary

The seminar focuses on the strut-and-tie method, a truss analogy approach introduced in 2002 as a solution when Bernoulli bending theory does not apply, such as in structures with geometric changes or openings. It replaced empirical equations for deep beams by relating member depth to span length, utilizing ties for tension, struts for compression, and nodes for joints. Changes for the 2019 ACI Building Code include handling shear and tension issues with a universal strength reduction factor of 0.75, and updates to bottle-shaped struts, now removed, and reinforcement requirements in disturbed regions (D regions).<br /><br />Minimum reinforcement requirements have been standardized, with orthogonal reinforcement in two directions or as one-dimensional for corbels. The seminar also covers integration with prestressing and post-tensioning, emphasizing force development, strut strength, and node detailing, with the recent inclusion of curved bar nodes to assist in areas like dapped-end beams. Applications for seismic design have emerged, necessitating detailing rules. Earthquake-resistant design further requires reduction factors for the effective strength of nodes and additional confinement for struts.

Keywords

strut-and-tie method

truss analogy

ACI Building Code

shear and tension

reinforcement requirements

prestressing

seismic design

earthquake-resistant